Endoscopes and endoscopic video cameras are now widely used by physicians during surgery to view inside body cavities. Typically, the endoscopic video camera contains an optical focusing lens, an optical zoom lens, and a focus and zoom device that can be adjusted to optimize images transmitted by the endoscope. After each use with a patient, the endoscope and endoscopic video camera must be cleaned and sterilized before they can be used again. Due to cost and time considerations, it is desirable to sterilize both endoscopes and endoscopic video cameras using high temperature steam autoclaving.
The focus and zoom device usually includes external adjuster assemblies (e.g. a focusing knob assembly and a zoom knob assembly), and usually utilizes magnetic drives to move or rotate the optical focusing lens and the optical zoom lens. In an effort to simplify the focus and zoom device, and to solve various shortcomings associated with complicated endoscopic video cameras in the prior art, U.S. Pat. Nos. 6,522,477 and 6,633,438, both issued to Anhalt, disclose endoscopic video cameras having at least one magnetizable lens that moves or rotates in response to the rotation of an external magnetic adjuster assembly. The external magnetic adjuster assemblies of Anhalt have the following components and structures, as illustrated in FIG. 1. An adjuster assembly 10 includes an adjuster (i.e. a knob) 11 having grooves 12 on its inside diameter, magnetic spacers 13, 14, and o-rings (not shown). The adjuster 11 carries magnets 15, which are positioned axially and radially by the grooves 12 and by the magnetic spacers 13, 14. The o-rings provide tension to hold the adjuster 11 in place between adjustments, while also easing the rotation of the adjuster 11 by hand. The adjuster 11 is metallic, preferably made of stainless steel.
FIG. 2 illustrates an alternative embodiment of a prior art external adjuster assembly, which is a zoom knob assembly for an endoscopic camera. In this embodiment, zoom knob assembly 20 has a hollow metallic outer zoom knob (i.e. adjuster) 21, a metallic inner ring 22, a spacer ring 23, and an internal o-ring 24. Outer zoom knob 21 has bosses 25, an interior surface 26, and a floor 27 joining bosses 25 and interior surface 26. Outer zoom knob 21 carries external magnets 28, which are positioned axially and radially by the grooves 29 in inner ring 22. Inner ring 22 is positioned between the bosses 25 and the interior surface 26 of outer zoom knob 21.
Traditionally, the external adjusters 11 and 21, spacers 23, and metallic inner ring 22 of FIGS. 1 and 2 are manufactured from solid metal bar stocks by 100% machining. After machining, the external adjusters and spacer rings are two-step anodized to a particular color according to the product requirements. Additionally, the assembly of the external adjuster assemblies of FIGS. 1 and 2 requires press fits between their respective components and structures. For example, referring to FIG. 2, zoom knob assembly 20 requires press fits between outer zoom knob 21 and the inner ring 22, and press fits between the spacer ring 23 and inner ring 22. The design and method of manufacturing these prior art external adjuster assemblies unavoidably results in high manufacturing costs in terms of the cost and amount of the metal used, machining time, anodizing costs, assembly time, and inspection time. Also, using this manufacturing method, it is difficult, if not impossible, to machine the external adjuster assemblies with consistent precision.
In recent years, metal injection molding (“MIM”) processes have been used to manufacture various components of medical or optical instruments, as disclosed in U.S. Pat. Nos. 6,514,269 and 7,718,100; and U.S. Pat. Appln. Nos. 2013/0012773 and 2006/0242813. The teachings of these references are incorporated herein by reference in their entirety. Compared to the traditional 100% machining and other techniques such as casting, stamping, and lithography, the MIM process reduces the amount of material used for manufacturing and allows a high volume production with reasonable consistency in quality. The MIM process is also versatile at producing small components having complex internal and external shapes.
One disadvantage of MIM processes is that they can require the application of several hundred tons of pressure to a mold, which results in high tooling costs. Additionally, the metal blanks that are used in the MIM processes are expensive and usually require a significant amount of “secondary machining” or “post machining” to achieve the desired high-precision dimensions of the final components. This manufacturing method therefore results in extremely high manufacturing costs for manufacturing external adjuster assemblies.
As an alternative to MIM processes, plastic injection molding (“IM”) processes have been used to manufacture various polymeric components of medical devices, as disclosed in U.S. Pat. No. 7,942,896 and U.S. Pat. Appln. No. 2006/0242813. Typically, plastic components are less costly than metal components. However, one problem with plastic injection molding processes is that they may leave undesirable molding characteristics on the outer cosmetic surfaces of the final product, such as visible flow marks, weld lines, knit lines, gate marks, sink marks, and ejection pin marks. Additionally, during the assembly of plastic components, an undesired layer of material, also known as “flash,” may escape to the outer cosmetic surfaces of the final product, and flash removal may be costly. Further, the cosmetic appearance of plastic components is typically not as visually appealing as metallic components, and polymeric components may have the tendency to degrade under high temperature steam autoclave sterilization.
What is needed, therefore, is an improved method of manufacturing medical device components, such as a zoom knob assembly or a focus knob assembly for an endoscopic camera, which utilizes plastic materials, shortens the overall manufacturing time, reduces the overall manufacturing cost, minimizes undesirable molding characteristics on the outer cosmetic surfaces of the components, and eliminates the need for flash removal. It is also desirable that the polymeric material used in such manufacturing method has a metallic appearance and withstands sterilization without showing signs of degrading. It is also desirable that such manufacturing method and polymeric material are sufficiently versatile to be applied to various types of medical device components.